Polyesters are polymers that contain a plurality of ester linkages. Polyesters are one of the most widely used polymers for commercial applications. In fact, after polyolefins, polyesters are the most widely used polymers for commercial applications. The most commonly used polyester is polyethylene terephthalate (PET). Other commonly used polyesters include polybutylene terephthalate (PBT), polybutylene succinate (PBS), polyethylene adipate (PEA), polycaprolactone (PCL), and polylactic acid (PLA).
In many cases, polyesters are formed from monomers that are derived from refining petroleum products. Such processes generally involve cracking and refining crude petroleum to obtain olefin fragments having a small number of carbon atoms (e.g., two or three carbons). To form longer-chain compounds, the fragments must be reacted to with other such fragments and/or other compounds to form compounds having longer carbon chains. This process is energy-intensive and time-intensive. Further, such processes contribute to the further depletion of non-renewable sources of carbonaceous material.
There are some exceptions, such as polylactic acid (PLA). In fact, PLA has the second highest consumption of any renewably derived polymer in use today. But its use is generally limited to situations where resistance to degradation is not an issue. For example, PLA is widely used in making biodegradable materials, such as medical implants, disposable cups, and the like. But there are a very limited number of polymers made from renewably derived monomers that exhibit chemical and physical characteristics closer to those of more commonly used polyesters.
Refining processes for natural oils (e.g., employing metathesis) can lead to compounds having carbon-chain lengths closer to those generally desired for chemical intermediates of specialty chemicals (e.g., about 9 to 15 carbon atoms). Thus, the refining of natural oils may, in many instances, provide a more chemically efficient and straightforward way to make certain monomers for use in making polymeric species, such as polyesters. Further, because such compounds contain a certain degree of inherent functionality that is otherwise absent from petroleum-sourced materials, it may often be more desirable, if not cheaper, to use natural oils or their derivatives as a starting point for making certain compounds. Additionally, natural oils and their derivatives are generally sourced from renewable feedstocks. Thus, by using such starting materials, one can enjoy the concomitant advantage of developing useful chemical products without consuming limited supplies of petroleum.
Thus, there is a continuing need to discover novel polyesters that are formed using monomers derived from renewable sources, such as natural oils.